To insulate a greenhouse for winter use, focus on reducing heat loss and maintaining a stable internal temperature. Double-layered polycarbonate or glass panels provide effective insulation while allowing sufficient light to enter. Applying bubble wrap to the inside walls and roof adds an extra layer of thermal protection without blocking sunlight.
Sealing gaps and cracks in the structure with weatherstripping or caulk prevents cold air infiltration. Insulating the north-facing wall with reflective or solid materials helps retain heat by reducing exposure to cold winds. Using thermal mass, such as water barrels or stone floors, stores heat during the day and releases it at night to stabilize temperatures.
